Bethany Mellmoth stands outside the No Parking Gallery in Dalston waiting for the owner and the gallerist, Howard Christopher, to open the door for her. He is always there, no matter how early she arrives, and sometimes she wonders if he lives in his office – though she knows full well he has a large house and large family (issue of three wives) in Victoria Park. "Coming, Bethany, darling," she can hear his deep voice calling from the back, somewhere. He is a friend of her mother – and it was this friendship that secured Bethany the job as a gallerina in No Parking. The gallery is named after a prominent "No Parking" sign set on the kerb outside its front door. Thinking about names, Bethany realises that Howard Christopher's name is in fact two Christian names. Funny that, she thinks, not having a proper surname.

Bethany goes down to Howard's basement office with his morning jug of fresh orange juice. They chat about the day's business – one exhibition leaving, preparing for another being installed – as Howard opens his fridge to take out the vodka bottle. He tops up his glass of orange juice with an inch or so of vodka. He waves the bottle at Bethany but she declines. Howard takes out a ready-rolled spliff from a cigarette case and lights up. "Very excited about the new show," he says. He looks at her, shrewdly: "You all right, lovely baby?" Bethany says she's fine, thanks.

In fact, Bethany is troubled this morning by something she read in a newspaper on her short but arduous bus journey to Dalston from Stoke Newington. The average lifespan of a human being, she had read, is around 1,000 months. This is entirely reasonable, she understands, and logical, but it has made her ill at ease. It doesn't seem nearly enough – somehow much worse than knowing one lives three-score years and 10. Seventy years seems improbably long. One thousand months appears almost terrifyingly brief. She does a quick calculation – she has already used up 272 months and what has she achieved in her life? Nothing.

Rod Hurt, the sculptor, supervises the deposition of his show. Bethany stands by his side with a clipboard as they go through the various works. "Bin it," Hurt says. "Bin it, bin it. Keep the wood. Bin it, bin it." Hurt's show was called "Missing". And what was missing was the artwork itself: there was a presentation of the raw material – a symbolic block of wood, a chunk of marble, pile of clay, sack of plaster, planks of driftwood, seashore pebbles and so forth. Hurt had made a sculpture from similar materials and had then destroyed it. So set beside the granite rock was a pile of granite chips, by the tree trunk a mound of wood shavings, a cone of ash by the driftwood, iron girder transformed to crushed steel ingot and so forth. Bethany had said to him at the show's opening that she kept trying to imagine what was in between. "Exactly, that's the point," Hurt said. "And what you imagined was probably better than what I did."

Seeing the wanton and carefree dismantling of Hurt's show has increased Bethany's angst. And it is "angst", she realises – genuine angst, not the blues or PMT or simply feeling fed up. She is going through a minor but compelling crisis of an ontological sort. The message of Hurt's absent artworks plus the knowledge that she has only around 700-odd months left of life on this planet has shaken her up, somewhat. She will be 23 soon and all she has to show for these years, these months, is a series of truncated false starts. Leaving college and abandoning her media studies course; failing to get into drama school; the novel she started and set aside, unfinished; her short, unhappy experience as a film extra – she could go on and on. Nothing seemed to click, or fit. Everything she dreamed of being appeared to stall, or she was distracted, or else other people messed it up. And look at her now – now she was a VARP, a "Vaguely Art-Related Person".

The VARP acronym was something else she'd read about and it made her unhappy. She had thought that becoming a gallerina might open doors, might help her with her photography project and the book she was planning to accompany it, but now she wondered if it was just another dead end. Still, at least the next show in No Parking was by a photographer, Fernando Benn, not that she'd heard of him. Perhaps this might be the opportunity she was waiting for.

On the walk from the bus stop after her day's "work" Bethany passes a derelict garage. In the middle of its forecourt a small plant seems to be growing out of concrete. She takes her camera out – a little digital Leica – and photographs it. It's a small, vigorous buddleia that has somehow managed to root itself, grow and flourish in a minute fissure. Bethany's photography project, and its eventual book, is a series of images of plants growing out of rocks – or bricks, or paving stones. It's called "Suffering from Optimism" and this shot of the buddleia in its patch of oil-stained garage forecourt might be perfect for the cover. She has many photos of buddleias – she marvels at how they seem to grow in impossible unnourished places, on roof edges, in dry gutters, in the grouting of brick walls. In fact the buddleia is probably her favourite flower.

Fernando Benn's show at No Parking is called "WAR"/WAR. It consists of a series of huge photographs, six feet by six, of famous war photographs: Robert Capa, Hubert Van Es, Don McCullin, Philip Jones Griffiths, Tim Page – all classic shots, almost all familiar to Bethany. Fernando Benn has cut them out of books, pinned them on his studio wall, photographed them so that they are framed by the background and blown them up. Benn is standing in the middle of the gallery idly supervising the hang. He's a man in his 40s wearing a leather jacket, jeans and red cowboy boots. He hasn't shaved for a few days. "Great, fantastic," he says. "No, no, leave it there. It's fine." Bethany asks him if she can get him a coffee or a water. "I'll have one of Howard's vodka and oranges," Benn says. When Bethany hands him his drink she senses him looking her up and down. "You're new," he says. "You weren't at No Parking for my last show. What's your racket, darling?" Bethany says she's interested in photography. "Photography is dead," Benn says with a cough-laugh. "Who was it who said that? Now we're in the digital age, photography has lost its veracity because it can be manipulated so easily – yeah? The photographic image has lost its power." But you're a photographer, Bethany says, unreflectingly, how can you say that? "I'm not a photographer," Benn says, a little wearily, "I'm an artist who chooses to work in lens-based media." He gestures at his photos. "These are digital pictures of photos shot on film. It's the only way they can achieve any power, any veracity." Benn favours the glottal stop in his conversation. He smiles at her. "Like a cannibal eating the brain of his enemy to make him stronger. Yeah?"

When Bethany arrives home that night, at the house in Stoke Newington where she lives with her boyfriend Kasimierz, she is still thinking about Fernando Benn's assertion and wondering therefore if her own project is rendered meaningless. Should she abandon "Suffering from Optimism"? Another dead end? She goes into the kitchen and lets out a little shriek of surprise and alarm. Ten swarthy men wearing jeans and T-shirts are sitting round the kitchen table eating food out of cartons. One man stands up and speaks to her – smilingly, amiably – in a language she doesn't understand or recognise. She gives him a wave, turns and goes upstairs to her and Kasimierz's bedroom and locks the door.

When Kasimierz comes home late that night, he explains. It's a new venture, he says, and it's going to make him a lot of money. He has bought 20 two-year-old Ford Mondeos at a car auction for £1,000 each. The men downstairs are his new drivers. With his drivers and his cars he is now in a position to bid for all the London borough contracts. "Council work," he tells her. "Now I can undercutting all English mini-cab firms by 50% – 60%, even. No competition." Bethany asks a few more questions. Yes, Kasimierz says, the men will be living here in the basement. "They have TV, they have food, they have bed and roof. They very happy. I paying them £1 per hour – four times what they do in their country." Kasimierz kisses her as if he senses her anxieties. "They will work 80 hours a week. You never see them." He outlines the future as he sees it: first 20 cars, then 40, then 200 – every London borough will be coming to him. "You must meet Chaz," Kasimierz says. Who's Chaz? "He is my Englishman. You must have an English for meetings and phone."

In No Parking Bethany sits at her small desk looking at Fernando Benn's photos of photos of men at war thinking of Kasimierz. This is what drew her to Kasimierz, she realises, it wasn't simply his rangy frame, his energy, his almost disturbingly pale pale-blue eyes. He achieved things. He made events conform to his wishes. He had ambitions and he realised them. She picks up the phone and calls him. She says her mother is unwell and she has to go home and look after her for a few days. "I text you, Bethany," Kasimierz says. "Take care."

Bethany hands in her notice the day "WAR"/WAR is due to open. Howard seems barely to register the news. "Fine, fine – give my love to your mother." As she's about to leave the room he calls her back. "It's nothing to do with that dirty bugger Neville, is it?" he asks. "Neville hasn't jumped on you or anything, has he? Made a pass?" Who's Neville, Bethany asks? "Neville Benn. Sorry, Fernando – I keep forgetting." No, no, Bethany says, nothing to do with Neville.

To celebrate her joblessness Bethany goes to a bar before catching a tube back to South Kensington where her mother lives. Her mother is pleased but also irritated to see her back at home again, Bethany can tell. Kasimierz has texted her a couple of times to ask if she's missing him. It's early evening and the bar is quiet. Bethany looks at the list of cocktails and orders one called a "Crack of Doom" – it has many powerful alcoholic ingredients, some with names she doesn't recognise. She wants to smoke a cigarette and think about her plan and is annoyed she can't. She has found a website called "Fli-leaf.com" where photographic books can be made. Fli-leaf.com supplies a format, you provide images and text and pay them £120. Two weeks later you receive a bound hardback book with glossy pages. Further books can be ordered at £20 each. "Suffering from Optimism" will be born at last, at last she – . Her thoughts are interrupted by the sight of the barman throwing a bottle to the ceiling and catching it behind his back. He balances the cocktail shaker on his knee and pours in liquor from a full arm's length away. He jams the cap on the shaker and spins it on a fingertip, then he juggles four shot glasses, snatches one and sets it in front of her, catches the other three at the same time and finally serves her the drink – it's a fizzing dark purple, with a dense orange froth. "Wait, I have to set it on fire," the barman says. "Just kidding. It's a cool drink. Don't get many requests for it." He's a small, stocky young guy, with a broad, open face. He has a thin stripe of beard running down his chin from his lower lip. He is clearly incredibly fit and muscled. Bethany is usually drawn to tall skinny guys but there's something about this person… That was amazing, she says, how did you learn to do that stuff? "I used to be a juggler," he says, "but there's no money in juggling. So I became a mixologist. All these tricks are very easy. Beginner's juggling – but it looks good in a bar." He smiles at her, Bethany can tell he likes her. I'm Bethany, she says. "I'm Hunter," he says. Is that your first name or your surname, Bethany asks? "Hunter Doig," he says. "Hunter's a first name in Scotland." Bethany sips her Crack of Doom – it's very strong. Hunter leans his muscled forearms on the bar. "So, Bethany," Hunter says, "what do you do?" Bethany pauses a moment, sets her drink down. I'm a photographer, she says.

Author of A Heartbreaking Work Of Staggering Genius and What Is The What: The Autobiography of Valentino Achak Deng, Eggers founded McSweeney's publishing house. He has recently co-written, with Spike Jonze, a film adaptation of Maurice Sendak's Where The Wild Things Are.